Aww, he is adorable!!
I've kept a couple with cotton coats with a full coat and their coats were very thick. I will tell you it is a lot of hard work and not really possible with around the house products. You have to use a good conditioner and some finishing products and it only lasts so long.
I now keep them in modified cuts much like Zhoie with the body cut very short and the legs and face long. This is what I would do if I were you. It's a lot easier to maintain but still gives that long coat illusion especially if you like to wear clothes on them. Plus they enjoy it too as that means less brushing for them and is much cooler for the warmer months.
The hair on the head you can usually tame much easier to achieve a look closer to the picture you posted of what you want. The hair on the body however is a different story.
Here is a picture of my yorkiepoo Trixie. She has a very thick cottony coat and for a long time I kept it full, it was to the ground. In this picture it wasn't full length but it kinda gives you an idea. The hair tends to be a bit less poofy the longer it is because the weight pulls the hair down but the poofyness never completely goes away.
As you can see the hair on her head isn't poofy. It never was, just thick.
TrixieBear 01.jpg
It was a lot of hard work and I noticed she would get hot easily so I then gave her this hair cut and she has been much happier.
If I was to put a shirt or dress on her you wouldn't ever know her hair was cut.
Trixie3.jpg